Some vehicles include assist handles disposed on an interior of a passenger compartment of the vehicle. A passenger may grasp the assist handle to aid in ingress and/or egress to and/or from the passenger compartment of the vehicle.
Some assist handle assemblies include a spring powered retractable handle. The handle automatically retracts out of the way into a stowed position when not in use. For use, the passenger grasps the handle and pulls the handle to an open position, at which time the passenger may leverage against the assist handle to aid in ingress and/or egress. Upon releasing the handle, a spring automatically biases the handle back into the stowed position. The assist handle may include a damper to slow the return of the handle back into the stowed position, thereby preventing the handle from quickly “snapping” back into the stowed position.
Typically, the spring that biases the handle back into the stowed position includes a torsion spring, e.g., a wound coil that stores energy when a torque is applied. However, torsion springs do not exhibit a uniform torque curve. For example, torsion springs provide more power when storing larger amounts of torque than when storing lesser amounts of torque. Accordingly, as the torsion spring unwinds, the power provided by the torsion spring decreases. As such, the torsion spring provides a higher power output when in the open position, and lower power output when in the stowed position.
Therefore, the torsion springs used in assist handles are sized to provide minimal power when the handle is in the stowed position to minimize the “snapping” of the handle. When so sized, the torsion springs tend to provide excessive power when the handle is in the open position. When used in combination with the damper, torque losses from the damper, especially if the torsion spring weakens over time, may reduce the available torque from the torsion spring to a level insufficient to fully return the handle back to the stowed position, commonly referred to as a “lazy handle”.